Year 691 (DCXCI) was a common year starting on Sunday (link will display the full calendar) of the Julian calendar. The denomination 691 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
|Ab urbe condita||1444|
|Balinese saka calendar||612–613|
|Chinese calendar||庚寅年 (Metal Tiger)|
3387 or 3327
— to —
辛卯年 (Metal Rabbit)
3388 or 3328
|- Vikram Samvat||747–748|
|- Shaka Samvat||612–613|
|- Kali Yuga||3791–3792|
|Minguo calendar||1221 before ROC|
|Seleucid era||1002/1003 AG|
|Thai solar calendar||1233–1234|
817 or 436 or −336
— to —
818 or 437 or −335
- King Theuderic III dies and is succeeded by his son Clovis IV, age 9, as sole ruler of the Franks. He becomes a puppet—a roi fainéant—of his uncle Pepin of Herstal, mayor of the palace of Austrasia.
- Battle of Maskin: An Umayyad army under caliph Abd al-Malik defeats the rebel forces in Mesopotamia (modern Iraq). He reconquers the Arabian Peninsula, taking the holy city of Medina.
- The Dome of the Rock is completed in Jerusalem (under the patronage of Abd al-Malik) during the Second Fitna, becoming the first work of Islamic architecture.
- Wilfrid, abbot of Ripon, tries to make himself bishop of all Northumbria. King Aldfrith seizes many of his Ripon Abbey estates, and proposes to create a bishopric there. Wilfrid is banished and flees to Mercia, where King Æthelred makes him bishop of Leicester.